JP5916403B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine accompanied by a blow-by gas recirculation device.

  Generally, a crank chamber of an internal combustion engine is isolated from a combustion chamber by a cylinder and a piston. However, this isolation is not perfect, and unburned gas leaks in the compression stroke of the internal combustion engine, and combustion gas leaks into the crank chamber through the gap between the cylinder and the piston in the expansion stroke. The leaked blow-by gas causes deterioration of the lubricating oil stored in the crank chamber and corrosion of the internal combustion engine body.

  For this reason, it has been common practice to implement a device for ventilating blow-by gas accumulated in the crank chamber. A general blow-by gas recirculation device (see, for example, Patent Document 1 below) includes a PCV passage that connects a crank chamber and an intake passage (in particular, a surge tank), and a PCV valve that opens and closes the PCV passage. Yes. The blow-by gas in the crank chamber is sent toward the intake passage via the PCV passage, is filled into the cylinder together with the intake air, and is finally recombusted in the combustion chamber. The PCV valve prevents backflow of blow-by gas and intake air from the intake passage toward the crank chamber.

  A mechanical PCV valve (see, for example, Patent Document 2 below) that separates an elastically biased valve body from a valve seat with a blow-by gas pressure basically has a differential pressure between a crank chamber and an intake passage. The larger the opening, the larger the opening. However, in a region where the differential pressure between the crank chamber and the intake passage is small, the opening degree is conversely reduced as the differential pressure increases. This characteristic is to stabilize the idling by securing the amount of fresh air that fills the cylinder during idle operation where the throttle valve opening is throttled and the above differential pressure is significantly increased by the intake negative pressure. This is what is needed.

  Fuel that temporarily stops fuel injection in a cylinder if the engine speed exceeds a certain condition when the driver requests to decelerate the accelerator pedal or release his foot from the accelerator pedal. Cut is executed.

  Unlike during idling, fuel is not burned during fuel cut, so there is no need to reduce the PCV valve opening. Nevertheless, when the mechanical PCV valve is adopted, the opening of the PCV valve is reduced during fuel cut, and the opportunity to ventilate the blow-by gas in the crank chamber has been lost.

  Needless to say, if an electromagnetic PCV valve (for example, see Patent Document 3 below) whose opening degree can be freely controlled by inputting a control signal from an ECU (Electronic Control Unit) is used, the PCV valve is cut during fuel cut. It is possible to ventilate the blow-by gas by increasing the opening. However, electromagnetic PCV valves are more expensive than mechanical ones.

Japanese Utility Model Publication No. 60-040812 JP 2007-231785 A JP 2009-221905 A

  An object of the present invention is to increase opportunities for ventilation of blow-by gas while using a mechanical PCV valve.

In the present invention, a PCV passage that communicates the inner chamber in which blow-by gas accumulates with the intake passage, and a PCV passage are provided to open and close, and when the pressure difference between the inner chamber and the intake passage is a predetermined value or less, the difference is provided. As the pressure increases, the flow rate of the blow-by gas flowing through the PCV passage increases. When the differential pressure between the inner chamber and the intake passage exceeds a predetermined value, the flow rate of the blow-by gas flowing through the PCV passage increases as the differential pressure increases. The internal combustion engine is controlled by a blow-by gas recirculation device having a mechanical PCV valve having a characteristic that decreases when the accelerator opening is below a threshold value and the fuel cut of the internal combustion engine is being executed. Then, the control apparatus for the internal combustion engine is configured to perform correction control for increasing the intake air amount so as to bring the differential pressure close to the predetermined value. Here, the inner chamber is a concept including a crank chamber in which blow-by gas is generated, a cam chamber communicating with the crank chamber, and the like.

  ADVANTAGE OF THE INVENTION According to this invention, the opportunity which ventilates blow-by gas can be increased, using a mechanical PCV valve.

The figure which shows the structure of the internal combustion engine and blow-by gas recirculation apparatus in one Embodiment of this invention. The figure which shows the flow volume characteristic of the mechanical PCV valve | bulb in the same embodiment.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. This internal combustion engine is a spark ignition type four-stroke engine. The internal combustion engine of the illustrated example is of an in-cylinder direct injection type, and includes a plurality of cylinders 1 (one of which is shown in FIG. 1), an injector 11 that injects fuel into each cylinder 1, An intake passage 3 for supplying intake air to each cylinder 1, an exhaust passage 4 for exhausting exhaust from each cylinder 1, an external EGR device 2 for recirculating EGR gas from the exhaust passage 4 toward the intake passage 3, It has.

  A spark plug 12 is attached to the ceiling of the combustion chamber of the cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes spark discharge between the center electrode and the ground electrode. The ignition coil is integrally incorporated in a coil case together with an igniter that is a semiconductor switching element.

  The intake passage 3 takes in air from the outside and guides it to the intake port of the cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 33, a surge tank 34, and an intake manifold 35 are arranged in this order from the upstream.

  The exhaust passage 4 guides the exhaust generated by burning the fuel in the cylinder 1 from the exhaust port of the cylinder 1 to the outside. A three-way catalyst 41 for exhaust gas purification is disposed on the exhaust passage 4.

  The external EGR device 2 realizes a so-called high-pressure loop EGR. The inlet of the external EGR passage is connected to a predetermined location upstream of the catalyst 41 in the exhaust passage 4. The outlet of the external EGR passage is connected to a predetermined location downstream of the throttle valve 33 in the intake passage 3, specifically to a surge tank 34. An EGR cooler 21 and an EGR valve 22 are provided on the external EGR passage.

  An ECU (Electronic Control Unit) 0 serving as a control device for an internal combustion engine according to the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface of the ECU 0 includes a vehicle speed signal a output from the vehicle speed sensor that detects the vehicle speed, a crank angle signal b output from the crank angle sensor that detects the rotation angle of the crankshaft and the engine speed, and the depression amount of the accelerator pedal. Alternatively, an accelerator opening signal c output from an accelerator opening sensor that detects the opening of the throttle valve 33 as an accelerator opening (so-called required load), the intake air temperature and the intake air in the intake passage 3 (particularly, the surge tank 34). An intake air temperature / intake pressure signal d output from a temperature / pressure sensor that detects atmospheric pressure, a battery voltage signal e output from a sensor that detects the voltage of the vehicle-mounted battery, and a water temperature sensor that detects the cooling water temperature of the internal combustion engine. Output from the cam angle sensor at multiple cam angles of the cooling water temperature signal f and intake camshaft or exhaust camshaft. A cam angle signal g that is, the ion current signal h or the like to be output from the circuit for detecting an ion current caused by the combustion of the mixture in the combustion chamber are inputted.

  From the output interface of the ECU 0, an ignition signal i for the igniter, a fuel injection signal j for the injector 11, an opening operation signal k for the electronic throttle valve 33, an opening operation signal l for the EGR valve 22, etc. Is output.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine via the input interface, and knows the intake pressure and the engine speed, and the cylinder 1 The amount of intake air charged into the engine is estimated, and the required fuel injection amount, fuel injection timing (including the number of fuel injections per combustion), fuel injection pressure, ignition timing, EGR amount (or EGR rate), and EGR Various operating parameters such as the opening of the valve 22 are determined. The ECU 0 applies various control signals i, j, k, and l corresponding to the operation parameters via the output interface.

  The blow-by gas recirculation device 6 in the present embodiment is for sending blow-by gas generated in the inner chambers 7 and 8 of the internal combustion engine to the intake passage 3, and includes a PCV passage 61, a PCV valve 62, and a blow-by passage 63. As an element.

  One end of the PCV passage 61 is connected to the crank chamber 7, and the other end is connected to the downstream side of the throttle valve 33 in the intake passage 3 (in particular, the surge tank 34), and the crank chamber 7 communicates with the intake passage 3. Let me. Blow-by gas in the crank chamber 7 is discharged to the intake passage 3 via the PCV passage 61.

  The PCV valve 62 increases or decreases the flow rate of blow-by gas flowing through the PCV passage 61. In the present embodiment, the PCV valve 62 is installed at a location where the PCV passage 61 is connected to the crank chamber 7. In this embodiment, the PCV valve 62 is displaced in a direction in which the valve body that is elastically biased and pressed against the valve seat is separated from the valve seat by the pressure of blow-by gas (against the elastic biasing force). This is a mechanical (differential pressure actuated) type valve.

  FIG. 2 shows the flow rate characteristics of the PCV valve 62. The PCV valve 62 is closed in a region A where the pressure in the intake passage 3 is equal to or higher than the atmospheric pressure (the intake pressure is a positive pressure), and prevents the reverse flow of blow-by gas or intake air through the PCV passage 61.

  In the region B where the pressure in the intake passage 3 is smaller than the atmospheric pressure (the intake pressure is negative) and the differential pressure between the pressure in the crank chamber 7 and the pressure in the intake passage 3 is not more than a predetermined value, the differential pressure is The larger the opening is, the larger the opening of the PCV valve 62 is, and the flow rate of blow-by gas flowing from the crank chamber 7 toward the intake passage 3 is increased.

  However, in the region C where the pressure in the intake passage 3 becomes very small (the intake negative pressure is very large) and the pressure difference between the crank chamber 7 pressure and the pressure in the intake passage 3 exceeds a predetermined value, the pressure difference Is larger, the opening degree of the PCV valve 62 is reduced, and the flow rate of blow-by gas flowing from the crank chamber 7 toward the intake passage 3 is reduced. When the pressure in the intake passage 3 is minimal (intake negative pressure is maximized), such as during idle operation or low load operation close to idle operation, the change in the flow rate of the PCV valve 62 with respect to the change in the intake passage 3 pressure changes. Become scarce.

  An oil separator (not shown) is interposed between the crank chamber 7 and the PCV valve 62. The oil separator has a labyrinth structure and performs a gas-liquid separation action for separating the lubricating oil contained in the flowing gas from the gas, and prevents the lubricating oil from being lost from the crank chamber 7.

  One end of the blow-by passage 63 is connected to the cam chamber 8 in the cylinder head cover of the internal combustion engine, and the other end is connected to the upstream side of the throttle valve 33 in the intake passage 3, and the cam chamber 8 communicates with the intake passage 3. Let me. An oil separator is also provided at a location where the blow-by passage 63 is connected to the cam chamber 8.

  When the PCV valve 62 is open, blow-by gas in the cam chamber 8 and the crank chamber 7 is sent out to the intake passage 3 via the PCV valve 62 and the PCV passage 61. At the same time, fresh air flows into the cam chamber 8 and the crank chamber 7 from the intake passage 3 via the blow-by passage 63, and the cam chamber 8 and the crank chamber 7 are ventilated. The blow-by gas returned to the surge tank 34 in the intake passage 3 is filled in the cylinder 1 and recombusted.

  The ECU 0 of the present embodiment executes a fuel cut that temporarily stops fuel injection from the injector 11 (and ignition by the spark plug 12) according to the driving situation. Normally, when the accelerator pedal depression amount is 0 or less than a threshold value close to 0 and the engine speed is equal to or higher than the fuel cut permission speed, the fuel cut is started assuming that the fuel cut condition is satisfied. The fuel cut permission rotational speed is higher than the target engine rotational speed during idling, so the internal combustion engine immediately before entering the fuel cut is not in an idling state.

  After the fuel cut is started, if any fuel cut end condition is satisfied, such as when the accelerator pedal depression amount exceeds the threshold value or the engine speed has decreased to the fuel cut return speed, the fuel cut ends. Then, the fuel injection (and ignition) is restarted. When the engine speed has decreased to the fuel cut return speed, the engine shifts to the idling state when the fuel cut is completed.

  Thus, the ECU 0 of the present embodiment corrects the intake air amount during the above-described fuel cut and increases the differential pressure between the crank chamber 7 internal pressure and the intake passage 3 internal pressure to a predetermined value, that is, the region shown in FIG. Correction control is performed so as to approach a value corresponding to the boundary (or the vicinity thereof) between B and region C. With this correction control, the opening degree of the PCV valve 61 during fuel cut is larger than that during idling operation or low load operation close thereto, and blow-by gas in the crank chamber 7 can be ventilated during fuel cut. Become.

  In the intake air amount correction control, the ECU 0 performs an operation for expanding the opening degree of the electronic throttle valve 33 to be larger than the opening degree determined based on the depression amount of the accelerator pedal. At this time, the amount of increase in the opening of the throttle valve 33 is set to be larger as the current engine speed is lower, and / or is set to be larger as the amount of depression of the accelerator pedal is smaller, for example. If the map data defining the relationship between the engine speed and / or the accelerator pedal depression amount and the opening amount of the throttle valve 33 is stored in advance in the memory of the ECU 0, the current engine speed and / or By searching the map using the accelerator pedal depression amount as a key, it is possible to know the amount of expansion of the throttle valve 33 to be realized.

  In the present embodiment, a PCV passage 61 that communicates the inner chambers 7 and 8 where blow-by gas accumulates and the intake passage 3 are provided, and a differential pressure between the inner chambers 7 and 8 and the intake passage 3 is provided to open and close the PCV passage 61. Is less than a predetermined value, the flow rate of the blowby gas flowing through the PCV passage 61 increases as the differential pressure increases, and the differential pressure between the inner chambers 7, 8 and the intake passage 3 is greater than or equal to the predetermined value. Is for controlling an internal combustion engine attached with a blow-by gas recirculation device 6 having a mechanical PCV valve 62 having a characteristic that the flow rate of the blow-by gas flowing through the PCV passage 61 decreases as the differential pressure increases. When the accelerator opening is equal to or smaller than the threshold value and the internal combustion engine is not in an idling state, correction control for increasing the intake air amount to correct the differential pressure to the predetermined value is performed. 0 to constitute a.

  In other words, in an operating state in which the pressure in the intake passage 3 is originally a negative pressure similar to that during idle operation, in particular, during fuel cut, the throttle valve 33 is intentionally opened so that the pressure in the crank chamber 7 and the intake passage 3 are increased. The differential pressure with respect to the internal pressure is reduced and the opening of the PCV valve 62 is increased to increase the flow rate of blow-by gas. According to this embodiment, the opportunity to ventilate the crank chamber 7 and the cam chamber 8 using the fuel cut period or the like can be increased without using an expensive electromagnetic PCV valve.

  Since the ventilation capacity of the blow-by gas in the crank chamber 7 is improved, the tension of the piston ring (seal between the combustion chamber and the crank chamber 7 by the piston ring, sliding friction between the piston ring and the bore wall of the cylinder 1) Since the reduction is allowed, it can contribute to the improvement of fuel consumption.

  The present invention is not limited to the embodiment described in detail above. For example, the PCV valve 62 is allowed to be installed at an arbitrary position on the PCV passage 61.

  Although the internal combustion engine in the above embodiment is a naturally aspirated engine, it is naturally possible to apply the present invention to an internal combustion engine accompanied by an exhaust turbocharger. In this case, the other end of the blow-by passage 63 that is an element of the blow-by gas recirculation device is connected upstream of the compressor of the supercharger in the intake passage 3. Compared to a naturally aspirated engine, in a turbo engine, the pressure in the intake passage 3 is often positive due to supercharging, and the time for opening the PCV valve 62 is shortened accordingly. The opportunity to ventilate the blow-by gas by opening the PCV valve 62 during the fuel cut accompanying the deceleration request can be secured.

  In the above-described embodiment, the opening degree of the electronic throttle valve 33 is operated to correct the increase / decrease in the intake air amount. However, in an internal combustion engine equipped with an idle speed control valve, the opening degree of the idle speed control valve is set. It may be operated to correct the intake air amount. As is well known, the idle speed control valve is a flow control valve that opens and closes a bypass passage that communicates the upstream side and the downstream side of the throttle valve in the intake passage.

  Further, during the intake air amount correction control, the control device 0 manipulates the opening of the electronic throttle valve 33 or the idle speed control valve so as to reduce the deviation between the actually measured value of the intake passage 3 pressure and the target value. The feedback control may be performed. The target value of the pressure in the intake passage 3 in this feedback control is the value of the intake negative pressure located at the boundary (or the vicinity thereof) between the region B and the region C shown in FIG.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
3 ... Intake passage 33 ... Electronic throttle valve 6 ... Blow-by gas recirculation device 61 ... PCV passage 62 ... PCV valve 63 ... Blow-by passage 7, 8 ... Inner chamber (crank chamber, cam chamber)

Claims (1)

A PCV passage communicating the inner chamber in which blow-by gas accumulates and the intake passage;
When the pressure difference between the inner chamber and the intake passage is less than a predetermined value, the flow rate of blow-by gas flowing through the PCV passage increases as the pressure difference between the inner chamber and the intake passage increases. When the differential pressure with respect to the passage is equal to or greater than a predetermined value, a blow-by gas recirculation device including a mechanical PCV valve having a characteristic that the flow rate of the blow-by gas flowing through the PCV passage decreases as the differential pressure increases is attached. Controlling an internal combustion engine,
Control of an internal combustion engine, wherein when the accelerator opening is equal to or less than a threshold value and the fuel cut of the internal combustion engine is being executed, correction control is performed to increase the intake air amount and bring the differential pressure closer to the predetermined value apparatus.

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